In general, a fuel cell refers to a power generation-type cell which produces electricity by bonding hydrogen and oxygen. The fuel cell may continuously produce electricity as long as hydrogen and oxygen are supplied, differently from general chemical cells, such as batteries or storage batteries, and have no heat loss, thus having efficiency twice that of an internal combustion engine. Further, the fuel cell converts chemical energy, generated by bonding hydrogen and oxygen, directly into electrical energy and thus discharges few pollutants. Therefore, the fuel cell is advantageous in that it is eco-friendly and reduces worries about resource depletion owing to increase in energy consumption. Fuel cells may be generally classified into a polymer electrolyte membrane fuel cell (PEMFC), a phosphoric acid fuel cell (PAFC), a molten carbonate fuel cell (MCFC), a solid oxide fuel cell (SOFC), an alkaline fuel cell (AFC), etc. according to kinds of electrolytes used. The respective fuel cells are basically operated by the same principle, but kinds of fuels used, operating temperatures, catalysts, electrolytes, etc. of the respective fuel cells are different. Thereamong, it is known that PEMFCs are operated at a low temperature, as compared to other fuel cells, have high power density, are small in size, and may thus be promising as not only small mounting-type power generation equipment but also transportation systems.
One of important factors to improve performance of the PEMFCs is to supply a designated amount or more of moisture to a polymer electrolyte membrane or a proton exchange membrane (PEM) of a membrane-electrolyte assembly (MEA) so as to maintain a desired water content. The reason for this is that, when the PEM is dried, power generation efficiency is rapidly decreased. In order to humidify the PEM, 1) a bubbler humidification method in which moisture is supplied by filling a pressure vessel with water and then causing target gas to pass through a diffuser, 2) a direct injection method in which an amount of supply moisture necessary for fuel cell reaction is calculated and then moisture is supplied directly to a gas flow pipe through a solenoid valve, and 3) a humidification membrane method in which moisture is supplied to a gas fluidized bed using a polymeric separation membrane. Thereamong, the humidification membrane method, in which vapor is fed to gas supplied to a polymer electrolyte membrane using a membrane selectively transmitting only vapor included in exhaust gas so as to humidify the polymer electrolyte membrane, is advantageous in that a humidifier may be lightweight and small.
As selectively transmitting membranes used in the humidification membrane method, hollow fiber membranes having a large transmission area per unit volume, if a module is formed, may be used. That is, if a humidifier is manufactured using hollow fiber membranes, high integration of the hollow fiber membranes having a large contact surface area is achieved and a fuel cell may be sufficiently humidified even at a small capacity of the humidifier, a low-cost material may be used, and moisture and heat included in unreacted gas of a high temperature discharged from the fuel cell may be collected and then reused through the humidifier.
However, a conventional hollow fiber membrane module has a short time for which a hot and humid humidifying fluid may directly contact hollow fiber membranes in the module and thereby have limits in raising heat/material transfer efficiency with a cool and dry fluid to be humidified and limits in enhancing humidifying efficiency of a product.
Further, in order to increase the capacity of hollow fiber membrane modules, technology in which a hollow fiber membrane bundle is partitioned or unit modules are integrated as cartridges is used. However, if such technology is used, a time taken to manufacture individual modules of the cartridges is long and thus manufacturing costs may be increased and, when the bundle is partitioned, workability in partitioning is lowered and thus quality variation may be increased.